In conventional inter-vehicle communication, only specific information about a vehicle is transmitted and received with a constant cycle. Further, based on that information, a display lamp or a buzzer provides information to a driver. However, when such information is provided, an approaching vehicle might advance to the same place. In order to cope with this problem, another vehicle that is predicted to affect traveling of an own vehicle is determined, and information about driver's intentions is bidirectionally transmitted or received between the own vehicle and the other vehicle (for example, see Patent Literature 1).